package day03;

import java.util.Scanner;

public class h3 {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            int score=scanner.nextInt();
            if(score>100){
                System.out.println("成绩不合法");
            }
            else if(score>=90){
                System.out.println("A");
            }
            else if(score>=80){
                System.out.println("B");
            }
            else if(score>=60){
                System.out.println("C");
            }
            else if(score>=0){
                System.out.println("D");
            }
            else {
                System.out.println("成绩不合法");
            }
        }
}
